How to fix GCC undefined reference to `sqrt’

Problem:

When trying to compile your application using gcc, you see an error message like

/usr/bin/ld: /tmp/ccxPIowU.o: in function `run_mymath':
mathstuff.c:(.text+0x15d): undefined reference to `sqrt'

Solution:

You need to link the math library using theĀ -lm flag (-lxxx means: “link the xxx library”, i.e. -lm means “link theĀ m” library)

For example, instead of

gcc -o myprogram *.c

use

gcc -o myprogram *.c -lm